Low Cost, Current Output
Temperature Transducer
TMP17
*
FEATURES
Operating Temperature Range: –40 C to +105 C
Single-Supply Operation: 4 V to 30 V
Excellent Repeatability and Stability
High Level Output: 1 A/K
Monolithic IC: Temperature In/Current Out
Minimal Self-Heating Errors
APPLICATIONS
Appliance Temperature Sensor
Automotive Temperature Measurement and Control
HVAC System Monitoring
Industrial Temperature Control
Thermocouple Cold Junction Compensation
GENERAL DESCRIPTION
FUNCTIONAL BLOCK DIAGRAM
NC
V+
V–
NC
NC
NC
NC
NC
PACKAGE DIAGRAM
SOIC-8
NC 1
V+ 2
8 NC
The TMP17 is a monolithic integrated circuit temperature trans-
ducer that provides an output current proportional to absolute
temperature. For a wide range of supply voltages, the transducer
acts as a high impedance temperature dependent current source
of 1
µA/K.
Improved design and laser wafer trimming of the
IC’s thin-film resistors allow the TMP17 to achieve absolute
accuracy levels and nonlinearity errors previously unattainable
at a comparable price.
The TMP17 can be employed in applications from –40 C to
+105 C where conventional temperature sensors (i.e., thermistor,
RTD, thermocouple, diode) are currently being used. Expensive
linearization circuitry, precision voltage references, bridge
components, resistance measuring circuitry, and cold junction
compensation are not required with the TMP17.
The TMP17 is available in a low cost SOIC-8 surface-mount
package.
PRODUCT HIGHLIGHTS
7 NC
TOP VIEW
V– 3 (Not to Scale) 6 NC
5 NC
NC 4
NC = NO CONNECT
4. The high output impedance of the TMP17 provides greater
than 0.5 C/V rejection of supply voltage drift and ripple.
5. Laser wafer trimming and temperature testing ensures that
TMP17 units are easily interchangeable.
6. Initial system accuracy will not degrade significantly over time.
The TMP17 has proven long term performance and repeat-
ability advantages inherent in integrated circuit design and
construction.
378
2. The TMP17 is electrically rugged; supply irregularities and
variations or reverse voltages up to 20 V will not damage
the device.
3. Because the TMP17 is a temperature dependent current
source, it is immune to voltage noise pickup and IR drops in
the signal leads when used remotely.
I
OUT
– A
1. A wide operating temperature range (–40 C to +105 C) and
highly linear output make the TMP17 an ideal substitute for
older, more limited sensor technologies (i.e., thermistors, RTDs,
diodes, thermocouples).
343
1 A/K
273
248
–45
–25
0
70
TEMPERATURE – C
105
125
*Protected
by U.S. Patent No. 4,123,698
Figure 1. Transfer Characteristic
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© 2003 Analog Devices, Inc. All rights reserved.
TMP17F/G–SPECIFICATIONS
(V = 5.0 V, –40 C
≤
T
≤
105 C, unless otherwise noted.)
S
A
Parameter
ACCURACY
TMP17F
TMP17G
TMP17F
TMP17G
POWER SUPPLY REJECTION RATIO
4 V < V
S
< 5 V
5 V < V
S
< 15 V
15 V < V
S
< 30 V
Nonlinearity
OUTPUT
Nominal Current Output
Scale Factor
Repeatability
Long Term Stability
POWER SUPPLY
Supply Range
Symbol
Conditions
T
A
= 25 C
1
T
A
= 25 C
1
Over Rated Temperature
Over Rated Temperature
Min
Typ
Max
±
2.5
±
3.5
±
3.5
±
4.5
0.5
0.3
0.3
Unit
C
C
C
C
C/V
C/V
C/V
C
µA
µA/
C
C
C/month
PSRR
PSRR
PSRR
Over Rated Temperature
2
T
A
= 25 C (298.2 K)
Over Rated Temperature
Note 3
T
A
= 150 C for 500 Hrs
4
+V
S
4
0.5
298.2
1
0.2
0.2
30
V
NOTES
1
An external calibration trim can be used to zero the error @ 25 C.
2
Defined as the maximum deviation from a mathematically best fit line.
3
Maximum deviation between 25 C readings after a temperature cycle between –40 C and +105 C. Errors of this type are noncumulative.
4
Operation at 150 C. Errors of this type are noncumulative.
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS*
METALLIZATION DIAGRAM
62mils
V+
Maximum Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . 30 V
Operating Temperature Range . . . . . . . . . . . –40 C to +105 C
Maximum Forward Voltage (1 to 2) . . . . . . . . . . . . . . . . . 44 V
Maximum Reverse Voltage (2 to 1) . . . . . . . . . . . . . . . . . . 20 V
Dice Junction Temperature . . . . . . . . . . . . . . . . . . . . . . 175 C
Storage Temperature Range . . . . . . . . . . . . . –65 C to +160 C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . . 300 C
*Stresses
above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only and functional operation at
or above this specification is not implied. Exposure to the above maximum rating
conditions for extended periods may affect device reliability.
37mils
V–
TEMPERATURE SCALE CONVERSION EQUATIONS
K
C
+223
–50
+273
0
+298
+25
+323
+50
+373
+100
+423
+150
ORDERING GUIDE
F –100
0
+32
5
( F – 32)
9
+100
+70
F=
9
C + 32
5
+200
+212
+300
Model
Max Cal
Error
@ +25 C
Max Error Nonlinearity
–40 C to
–40 C to
Package
+105 C
+105 C
Option
3.5 C
4.5 C
0.5 C
0.5 C
R-8
R-8
C=
K = C + 273.15
TMP17FS 2.5 C
TMP17GS 3.5 C
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although the
TMP17 features proprietary ESD protection circuitry, permanent damage may occur on devices
subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended
to avoid performance degradation or loss of functionality.
–2–
REV. A
Typical Performance Characteristics–TMP17
6
5
V+ = +5V
4
TEMPERATURE ERROR – C
1
3
2
1
0
–1
–2
4
–3
–4
–5
–6
–50
–25
0
MIN LIMIT
25
50
TEMPERATURE – C
75
100
125
5
2
3
MAX LIMIT
500
450
400
CONSTANT I
OUT
UP TO 30V
I
OUT
= 378 A
OUTPUT CURRENT – A
350
I
OUT
= 298 A
300
250
T
A
= +105 C
200
150
100
T
A
= –40 C
50
0
0
1
2
3
4
SUPPLY VOLTAGE – V
5
6
T
A
= +25 C
I
OUT
= 233 A
TPC 1. Accuracy vs. Temperature
TPC 4. V-I Characteristics
100
90
80
PERCENT OF CHANGE – %
70
60
50
40
30
20
10
0
0
5
10
15
TIME – sec
V+ = +5V
SOIC PACKAGE
SOLDERED TO
0.5" 0.3" Cu PCB
2µs
100
90
V
IN
= 0V TO 5V
R
L
= 1k
T
A
= 25 C
10
0%
200mV
20
25
30
TPC 2. Thermal Response in Stirred Oil Bath
TPC 5. Output Turn-On Settling Time
60
TRANSITION FROM 100 C STIRRED
BATH TO FORCED 25 C AIR
50
TIME CONSTANT – sec
V
=
5V
SOIC PACKAGE SOLDERED
TO 0.5“ 0.3” Cu PCB
40
30
20
10
0
0
100
200
300
400
AIR VELOCITY – FPM
500
600
TPC 3. Thermal Time Constant in Forced Air
REV. A
–3–
TMP17
THEORY OF OPERATION
0.2
The TMP17 uses a fundamental property of silicon transistors
to realize its temperature proportional output. If two identical
transistors are operated at a constant ratio of collector current
densities, r, then the difference in base-emitter voltages will be
(kT/q)(ln r). Since both k, Boltzmann’s constant, and q, the
charge of an electron, are constant, the resulting voltage is
directly Proportional to Absolute Temperature (PTAT). In the
TMP17, this difference voltage is converted to a PTAT current
by low temperature coefficient thin film resistors. This PTAT
current is then used to force the total output current to be pro-
portional to degrees Kelvin. The result is a current source with
an output equal to a scale factor times the temperature (K) of
the sensor. A typical V-I plot of the circuit at 125 C and the
temperature extremes is shown in TPC 4.
Factory trimming of the scale factor to 1
µA/K
is accomplished at
the wafer level by adjusting the TMP17’s temperature reading
so it corresponds to the actual temperature. During laser trim-
ming, the IC is at a temperature within a few degrees of 25 C
and is powered by a 5 V supply. The device is then packaged and
automatically temperature tested to specification.
FACTORS AFFECTING TMP17 SYSTEM PRECISION
0.1
NONLINEARITY – C
TYPICAL NONLINEARITY
0
–0.1
–0.2
–0.3
–40
–25
0
25
TEMPERATURE – C
70
105
Figure 2. Nonlinearity Error
TRIMMING FOR HIGHER ACCURACY
Calibration error at 25 C can be removed with a single tem-
perature trim. Figure 3 shows how to adjust the TMP17’s scale
factor in the basic voltage output circuit.
+V
+
The accuracy limits in the Specifications table make the TMP17
easy to apply in a variety of diverse applications. To calculate a
total error budget in a given system, it is important to correctly
interpret the accuracy specifications, nonlinearity errors, the
response of the circuit to supply voltage variations, and the effect
of the surrounding thermal environment. As with other electronic
designs, external component selection will have a major effect
on accuracy.
CALIBRATION ERROR, ABSOLUTE ACCURACY, AND
NONLINEARITY SPECIFICATIONS
TMP17
–
+
R
100
950
–
V
OUT
= 1mV/K
Figure 3. Basic Voltage Output (Single Temperature Trim)
The TMP17 has a highly linear output in comparison to older
technology sensors (i.e., thermistors, RTDs, and thermocouples),
thus a nonlinearity error specification is separated from the
absolute accuracy given over temperature. As a maximum deviation
from a best-fit straight line, this specification represents the only
error that cannot be trimmed out. Figure 2 is a plot of typical
TMP17 nonlinearity over the full rated temperature range.
TOTAL ERROR – C
Two primary limits of error are given for the TMP17 such that
the correct grade for any given application can easily be chosen
for the overall level of accuracy required. They are the calibration
accuracy at +25 C and the error over temperature from –40 C
to +105 C. These specifications correspond to the actual error
the user would see if the current output of a TMP17 were
converted to a voltage with a precision resistor. Note that the
maximum error at room temperature or over an extended range,
including the boiling point of water, can be read directly from
the Specifications table. The error limits are a combination of
initial error, scale factor variation, and nonlinearity deviation
from the ideal 1
µA/K
output. TPC 1 graphically depicts the
guaranteed limits of accuracy for a TMP17GS.
To trim the circuit, the temperature must be measured by a refer-
ence sensor and the value of R should be adjusted so the output
(V
OUT
) corresponds to 1 mV/K. Note that the trim procedure
should be implemented as close as possible to the temperature
for which highest accuracy is desired. In most applications, if a
single temperature trim is desired, it can be implemented where
the TMP17 current-to-output voltage conversion takes place
(e.g., output resistor, offset to an op amp). Figure 4 illustrates
the effect on total error when using this technique.
1.0
ACCURACY
WITHOUT TRIM
0.5
0
AFTER SINGLE
TEMPERATURE
CALIBRATION
–0.5
–1.0
–40
–25
0
25
TEMPERATURE – C
105
Figure 4. Effect of Scale Factor Trim on Accuracy
–4–
REV. A
TMP17
If greater accuracy is desired, initial calibration and scale factor
errors can be removed by using the TMP17 in the circuit of
Figure 5.
97.6k
R2
5k
+5V
8.66k
REF43
7.87k
R1
1k
under several conditions. Table I shows how the magnitude of
self-heating error varies relative to the environment. In typical
free air applications at 25 C with a 5 V supply, the magnitude of
the error is 0.2 C or less. A small glued-on heat sink will reduce
the temperature error in high temperature, large supply voltage
situations.
Table I. Thermal Characteristics
OP196
+
+
V
OUT
= 100mV/ C
–
Medium
Still Air
Moving Air @ 500 FPM
Fluorinert Liquid
JA
( C/W)
(sec)*
52
10
2
TMP17
–
V–
Figure 5. Two Temperature Trim Circuit
158
60
35
With the transducer at 0 C, adjustment of R1 for a 0 V output
nulls the initial calibration error and shifts the output from K to C.
Tweaking the gain of the circuit at an elevated temperature by
adjusting R2 trims out scale factor error. The only error remaining
over the temperature range being trimmed for is nonlinearity.
A typical plot of two trim accuracy is given in Figure 6.
0.2
*
is an average of one time constant (63.2% of final value). In cases where the
thermal response is not a simple exponential function, the actual thermal
response may be better than indicated.
Response of the TMP17 output to abrupt changes in ambient
temperature can be modeled by a single time constant expo-
nential function. TPC 2 and TPC 3 show typical response time
plots for media of interest.
The time constant, , is dependent on
JA
and on the thermal
capacities of the chip and the package. Table I lists the effective
(time to reach 63.2% of the final value) for several different
media. Copper printed circuit board connections will sink or
conduct heat directly through the TMP17’s soldered leads.
When faster response is required, a thermally conductive grease
or glue between the TMP17 and the surface temperature being
measured should be used.
MOUNTING CONSIDERATIONS
0.1
TOTAL ERROR – C
0
–0.1
–0.2
–0.3
–40
–25
0
25
TEMPERATURE – C
75
105
Figure 6. Typical Two Trim Accuracy
SUPPLY VOLTAGE AND THERMAL ENVIRONMENT
EFFECTS
If the TMP17 is thermally attached and properly protected, it can
be used in any temperature measuring situation where the maxi-
mum range of temperatures encountered is between –40 C and
+105 C. Thermally conductive epoxy or glue is recommended
under typical mounting conditions. In wet environments, conden-
sation at cold temperatures can cause leakage current related errors
and should be avoided by sealing the device in nonconductive
epoxy paint or conformal coating.
APPLICATIONS
The power supply rejection characteristics of the TMP17 mini-
mize errors due to voltage irregularity, ripple, and noise. If a
supply is used other than 5 V (used in factory trimming), the
power supply error can be removed with a single temperature
trim. The PTAT nature of the TMP17 will remain unchanged.
The general insensitivity of the output allows the use of lower
cost unregulated supplies and means that a series resistance of
several hundred ohms (e.g., CMOS multiplexer, meter coil
resistance) will not degrade the overall performance.
The thermal environment in which the TMP17 is used determines
two performance traits: the effect of self-heating on accuracy and
the response time of the sensor to rapid changes in temperature.
In the first case, a rise in the IC junction temperature above the
ambient temperature is a function of two variables: the power
consumption level of the circuit and the thermal resistance
between the chip and the ambient environment (
JA
). Self-heating
error in
°C
can be derived by multiplying the power dissipation
by
JA
. Because errors of this type can vary widely for surroundings
with different heat sinking capacities, it is necessary to specify
JA
Connecting several TMP17 devices in parallel adds the currents
through them and produces a reading proportional to the average
temperature. TMP17s connected in series will indicate the lowest
temperature, because the coldest device limits the series current
flowing through the sensors. Both of these circuits are depicted
in Figure 7.
+15V
+5V
+
TMP17
+
–
+
–
+
–
+
TMP17
–
–
+
TMP17
TMP17
333.3
(0.1%)
V
T
AVG
(1mV/1K)
–
10k
(0.1%)
V
T
AVG
(10mV/1K)
Figure 7. Average and Minimum Temperature
Connections
REV. A
–5–
微控制器 MCU
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